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H. Peter Anvin wrote:
> Followup to: <20051016005341.GB5946@plexity.net>
> By author: Deepak Saxena <dsaxena@plexity.net>
> In newsgroup: linux.dev.kernel
>
>>It's a magic regsiter we just read/write and could be done in userspace.
>>I also took a look at MPC85xx and it has the same sort of interface but
>>also has an error interrupt capability. On second thought a class
>>interface is overkill b/c there will only be one RNG per system, so
>>I can just do something like watchdogs where we have a bunch of simple
>>drivers exposing the same interface. We could do it in user space but
>>then we have separate RNG implementations for x86 and !x86 and I'd
>>rather not see that. Can we move the x86 code out to userspace and
>>just let the daemon eat the numbers directly from HW? We can mmap()
>>PCI devices, but I don't know enough about x86 to say whether msr
>>instructions can execute out of userspace (or if we want them to...).
> MSR instructions cannot execute out of userspace, but the MSR driver
> might be possible to use. It's usually quite slow, however.
MSRs are used for setup, not for actual data.
Intel: magic MMIO address (readb)
AMD: magic PIO address (inl)
VIA: CPU instruction ('xstore')
Jeff
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